An improved small-angle X-ray scattering analysis of δ′ precipitation in Al-Li alloy with hard-sphere interaction

Abstract

Al-Li alloys are of particular interest for the aircraft industry, due to their low density and high strength. Precipitation of the alloy results in hardening of the material, which is of great technological importance. During the coarsening stage of {delta}{prime} precipitation the particles have a wide size distribution (polydisperse form). The interparticle interference effect in the small-angle X-ray scattering (SAXS) intensities arose from the high volume fraction of {delta}{prime} precipitates, and it makes the SAXS analysis much more difficult. So recent SAXS studies for Al-Li alloys still analyze the SAXS data by using either average radius (monodisperse form) or presumed size distribution, and a hard-sphere interaction model for the {delta}{prime} particle interference effect. In the work, an improved algorithm is developed to reconstruct the particle size distribution from SAXS intensities without any prior assumed size distribution. The hard-sphere interaction effect is also combined in the calculation. This method will be tested by analyzing simulated SAXS data and show an advantage in comparison with the other method. Then, it is used to reconstruct the particle size distribution from SAXS intensities without any prior assumed size distribution. The hard-sphere interaction effect is also combined in the calculation. This method will be testedmore » by analyzing simulated SAXS data and show an advantage in comparison with the other method. Then, it is used to reconstruct the particle size distribution of {delta}{prime} precipitates by analyzing a set of experimental SAXS data from Al-9.7 at% Li alloy having strong correlation peak, which results from inter-particle interference effect. More accurate parameters about structure and thermodynamic information can be extracted by employing the new method. The results of the analysis are also compared with the asymmetric size distribution model given by a growth kinetics theory, called modified Lifshiftz-Slyozov-Wagner (MLSW) theory.« less